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Jupiter Enters Prime Time

Topic: Jupiter
Article Published - February 9
by Dr. Jim Lattis, Director, UW Space Place
Jupiter in December

After a dearth of planet-viewing opportunities in recent months, Jupiter rides to our rescue. Our largest planet approaches its nearest and brightest moment, which astronomers call opposition, in early February (on the 6th to be precise). The moment of opposition itself is not very important, because Jupiter is big and bright for weeks before and after. At the same time, the planet is rising ever earlier in the eastern sky, which will make February and March a great time to get out for some early evening star gazing. Jupiter is easy to identify because, aside from the moon, it is the brightest object in the evening sky. But it also holds a distinctive position among the other brilliant objects in the mid-winter sky. Looking east in the early evening, as in the diagram above, imagine looking at a vast celestial pyramid. (The entire pyramid will shift westward in the course of the night, so later at night look more southward, then southwestward still later.) The base of the pyramid is outlined by Jupiter on the left corner, Sirius, the brightest star in the night sky, at the nearest corner, and Rigel, one of Orion's knees, at the right corner. The apex of the pyramid is marked by Capella, in Auriga, also one of the brightest stars in the sky. The faces of the pyramid are dotted with other bright stars, such as Betelgeuse in Orion, and over in Gemini are Castor and Pollux, the twins or Dioscuri of ancient Italic and Greek mythology who were, apropos our subject, sons of Jupiter.

This will also be a good time to think about getting out a telescope or binoculars to examine Jupiter. It's best to mount your binoculars on a tripod for astronomical viewing, but if you hold them steady enough, you should be able to see the Jovian entourage, the four moons we call the Galilean moons in honor of their discoverer, Galileo Galilei, who found them with a homemade telescope in 1610. Almost any small telescope (definitely on a tripod) will reveal the Galilean moons too. Compare their motions night by night, even hour by hour, and you will see them orbit their planet. Their motion around Jupiter, which showed that not everything in the universe moved around Earth, was a major factor in the Seventeenth-Century revolution in thought about the structure of our universe.

From the University of Wisconsin's "Space Place"
Villager Mall, 2300 S Park Street, Madison



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